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 A101794 Numbers k such that 4*k-1, 8*k-1, 16*k-1 and 32*k-1 are all primes. 10
 45, 90, 675, 885, 3030, 4290, 6870, 13410, 14460, 15855, 17850, 18675, 20625, 21885, 25350, 26820, 26925, 28230, 30525, 30705, 31710, 31785, 33375, 34860, 41685, 41940, 57435, 63420, 63570, 71805, 74025, 78585, 83865, 85230, 93075 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE 4*45-1 = 179, 8*45-1 = 359, 16*45-1 = 719 and 32*45-1 = 1439 are primes, so 45 is a term. MATHEMATICA Select[Range[10^5], And @@ PrimeQ[2^Range[2, 5]*# - 1] &] (* Amiram Eldar, May 13 2024 *) PROG (PARI) is(k) = isprime(4*k-1) && isprime(8*k-1) && isprime(16*k-1) && isprime(32*k-1); \\ Amiram Eldar, May 13 2024 CROSSREFS Cf. A002515, A101795, A101796, A101797, A101798. Subsequence of A005099, A005122 and A101790. Subsequence: A101994. Sequence in context: A184540 A115827 A070002 * A124017 A121925 A044183 Adjacent sequences: A101791 A101792 A101793 * A101795 A101796 A101797 KEYWORD easy,nonn AUTHOR Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 16 2004 STATUS approved

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Last modified June 13 22:21 EDT 2024. Contains 373391 sequences. (Running on oeis4.)